The best feature of having an action is that you can extend the logic of your program in another language, so you do not have to create a separate function / function block for that purpose.

For example:

Using the file handling command FILE_READ

In the POU we can configure the FILE_READ in the FBD logic. However when the data reading is complete, and if we like to perform some data sorting logic on the stored data, we can implement sort logic ACTION in the ST language. The ST is more convinient to create the mathematical manipulations.

By this we have a seperate logic which shares the POUs variable and can be called in teh POU simply by its name.